INCIDENCE OF OVULATORY CYCLES IN WOMEN APPROACHING THE MENOPAUSE

Urine was collected at weekly intervals for three or more months from 139 menstruant women aged 40-55 years. Menstrual cycles were classed as ovulatory if the 24-hr pregnanediol output was ≥ 5 μ mol on a single occasion, or if the total excreted on 2 days 1 week apart was ≥ 7 μ mol. Of the 81 women who reported no change in menstrual frequency, 95% ovulated in every cycle. Only 34% of the 53 with a recent history of oligomenorrhoea ovulated without fail. Ovulation occurred in 93% of all 21-35-day menstrual cycles, in 55% of 36-50-day cycles, in 40% of 51-75-day cycles and in 17% of those lasting ≥ 76 days. Pregnanediol increases suggestive of ovulation and followed by menstruation were observed on 31 occasions after amenorrhoea of from 2 to 6 months' duration. © 1979, North American Conference of British Studies. All rights reserved.